Crank Fasteners, OUCH!

Re-assembled the crank after cleaning and grind to +.020 on the 750 re-build. I have always used new bolts, studs and nuts even though most reference sources state you can get away with only replacing the nuts. On this occasion I did just that (couldn't wait for the bolts to arrive) my bad, while tightening the last bolt I felt a slight give (for want of a better description) Ouch, things could have ended real bad.
Note to self, never, never be a cheap SOB, replace the lot.
On the phone to place an order, will take a week to come from New Zealand but I dodged a bullet.
These things are over 40 years old, for the sake of around $90 investment, its cheap insurance not to mention the piece of mind.
JUG

Hi jug.
What was the "...slight give..."? and Cause?
Ta.

Hard to explain really, felt like stretch maybe. Still tight but just didn't feel right, felt like if I gave it another tweek it would snap. Went with my gut and ordered a set from NZ.
JUG

Well do not keep us on edge of seats, twist it the the rest of the way to get it out our systems and make plain what your spider sense registered. These crank fasteners are on sale scale of desired stretch as rod bolts .006-.0065 depending on ones take of various references, so I measured those I could and tried to repeat on those I could not. Unless the fastener was over torqued before you about only thing that could weaken it is a surface scratch that let corrosion work across grains.

A GREAT many years ago I took all the new crank bolts / studs in a friends shop stock out of the drawers and ran a micrometer over them....a great many were under size.They had come from several dubious(?) well known sources whose company names I will not mention......(Norton produced ones were correct size).
The Norton Dominator crank was designed such that at least one of the two fixing studs above the big ends had to be, according to Mr Hopwood's letter to me on the subject, a tight fit in both the crank halves and the flywheel. A friend who has probably built more Dommy and Commando engines for road and race use than probably most other people in this World always checks crank alignment and usually finds the big ends anything around 10 thou out of line with each other. He puts the crank together using slightly under size studs ensuring the big ends are correctly positioned and then removes one of the outer studs by the big ends and reams the hole to the next size ..8mm or 3/8 inch and fits a slight interference fit stud before doing it again to the other outer stud hole. My ex plod Mk2A crank was over 0.010 inch out on the big ends when checked..... Personally I doubt one big end out of alignment to the other makes much of a difference to the vibes produced by two pistons going up and down together but if you are going to have your crank apart you might as well put it together correctly AND at the same time look up the inside of the D.S half to see if the idiots at NVT / AMC have left that perfect example of a stress raiser(the sharp corner left by a big drill) directly beneath the big ends outer 90 thou stress reducing radius which is there to reduce the stresses at these change of section points of high stress to ensure the cranks stay as 3 piece which is rather a waste of time when directly beneath it is a perfect example of a stress raiser........... A friend and I had a few D.S. halves checked by a certain aircraft manufacturer and two of them were cracked and went straight in the scrap bin...not that the cracks were visible to th naked eye.
Unfortunately the Senior Metallurgist who looked at our broken drive side crank half and reported it had been slowly cracking over a long period before finally going BANG (at Oulton Park) is no longer alive and able to lecture others on stress raisers as he did me...well G.E.C. were paying for the phone call and our time which was jolly decent of them.....don't think the short term profit and no long term future accuntants who eventually successfully destroyed the company would of approved.... The book 'Engineer to Win' covers stress raisers well enough for our needs but DONT think of buying a copy... on the Abe Books web site copies are seriously well over £100 ...mine when new cost £14.95 and the other two books in the series(Prepare to Win and Tune to Win cost £12.95!!) OOPS just looked up Tune to Win on Abe Books...cheapest copy is £6 odd and the dearest £64..... Best borrow a copy from your local library assuming you still have one in your local area!! Just remember Comet airliners fell out of the sky due to a stress raiser and early construction Liberty ships broke in two thanks to a stress raiser and a great many innocent people are now dead or seriously injured due to them!!......and I have had two cranks fail due to the stress raiser some IDIOT left inside it during manufacture!!It was only when I looked at the second failure and thought the markings at the point of failure looked identical that I 'wondered' and had the broken crank checked out by our Senior Metallurgist up in our Gateshead works that I learnt about stress raisers. Better that YOU find it and get the crank checked and if still OK then get the stress raiser removed and polished out BEFORE YOUR CRANK GOES BANG. It's a LOT cheaper than a new crank, rods, pistons, probable barrel and even a cylinder head etc especially if the crank goes bang at 7,000 rpm!!

I thought Liberty ships broke up due to hydrogen embrittlement due to welding in a high humidity environment.

Very interesting, will check the DS when I separate the crank halves when the new fittings arrive. Never to old to learn.
JUG